JP2542930B2 - Voltage synthesizer type receiver - Google Patents

Description

The present invention relates to a voltage synthesizer type receiver,
The present invention relates to receiving devices such as radios, television receivers, and wireless receivers whose tuning tuning method is a voltage synthesizer method.

[Prior art]

Tuning methods for tuning a receiving device such as a television receiver are roughly classified into a frequency synthesizer method and a voltage synthesizer method.

[Problems to be Solved by the Invention]

Voltage synthesizer receivers have the advantage of being cheaper than frequency synthesizer receivers, but voltage synthesizer receivers do not have an absolute reference frequency like frequency synthesizer receivers, so the reception channel is automatically displayed. It had the drawback of not being able to do it.

Therefore, a main object of the present invention is to provide a voltage synthesizer type receiver capable of automatically displaying a channel number during reception.

[Means for solving the problem]

Briefly stated, the present invention is a voltage synthesizer type receiving apparatus for controlling the oscillation frequency of a local oscillator of a tuner unit by a tuning voltage according to control data from a microcomputer. In a microcomputer, there is provided a frequency dividing means for dividing by a ratio, a counting means for counting the frequency division output from the frequency dividing means, and a correlation table provided in association with the microcomputer for frequency and channel number data. A voltage synthesizer type receiving apparatus, characterized in that a channel number of a receiving channel at that time is displayed by referring to a correlation table based on the data counted by the counting means.

[Action]

The local oscillator included in the tuner unit is controlled by a tuning voltage obtained from, for example, a low-pass filter based on control data from the microcomputer, such as a PWM (pulse width modulation) signal. This local oscillation signal is frequency-divided by the frequency dividing means, and the frequency of the frequency-divided signal is counted by the counting means. On the other hand, in the correlation table between the frequency and the channel number data, which channel number the count value of the counting means corresponds to is stored in advance for each channel. Therefore, the microcomputer can obtain the channel number data being received at that time by referring to the correlation table based on the count data of the counting means. Then, this channel number is displayed, for example, on a display provided in the operation unit of the receiving device.

〔The invention's effect〕

According to the present invention, even if the voltage synthesizer system is used, the channel number being received can be automatically displayed. Therefore, it is advantageous in that it is cheaper than the frequency synthesizer system and is easy to use. A receiver is obtained.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

〔Example〕

Referring to FIG. 1, the receiving apparatus of this embodiment includes a tuner unit 12 that receives a broadcast wave or a radio wave received from an antenna 10. And in this tuner section 12, RF
The received signal from the amplifier 14 is input to the mixer 16 where it is mixed with the local oscillator signal from the local oscillator 18. This mixer
The 16 outputs are provided as IF (intermediate frequency) signals to the subsequent IF circuit (not shown). And from that IF circuit
The AFT circuit 20 controls the local oscillator 18 in response to the AFT signal.

The tuner unit 12 includes an ECL prescaler 22 composed of, for example, a 7-bit binary counter. As the ECL prescaler 22, for example, "M54487FP" manufactured by Mitsubishi Electric Corporation can be used. The signal divided by the ECL prescaler 22 is input to the counter 24. The counter 24 counts the frequency of the signal output from the ECL prescaler 22. Then, the count data from the counter 24 is given to the tuning microcomputer 26.

EEROM28 in connection with the tuning microcomputer 26
The EEROM 28 includes a correlation table (not shown) that is stored in advance for each channel as to which channel the frequency counted by the counter 24 corresponds to. In the case of television broadcasting in Japan, for example, the local oscillation frequency of 150.0 MH _Z corresponds to one channel, so this correlation table is stored in combination with this 150.0 MH _Z and one channel. Such pairs of frequency data and channel number data are stored in all channels. Incidentally, a reset signal and an enable signal are given from the tuning microcomputer 26 to the counter 24, and the count 24 receives the signal from the ECL prescaler 22 while the enable signal is given after the reset signal is given. Count frequencies.

The tuning microcomputer 26 outputs PWM signal data as control data according to the count data from the counter 24, and the PWM signal is tuned according to the PWM signal data from the low-pass filter 30 according to the PWM signal data. The voltage Vt is applied to the local oscillator 18.

Further, the tuning microcomputer 26 has an operation unit 32.
Position indicator 34 and channel indicator 36 included in
The display data is given to each.

In operation, the user operates a search switch (not shown) included in the operation unit 32. In response, the tuning microcomputer 26 outputs PWM signal data so as to gradually increase or decrease the tuning voltage Vt. Therefore, the oscillation frequency of the local oscillator 18 of the tuner unit 12 continuously changes.

Then, when tuning to the broadcast channel and the best tuning point is obtained by the AFT circuit 20, the tuning microcomputer 26 judges this. In response, the tuning microcomputer 26 outputs a reset signal and an enable signal to the counter 24. Therefore, the counter 24 counts the frequency of the output signal from the ECL prescaler 22. The counter 24 continues its counting operation until the enable signal is turned off, and the count data is input to the tuning microcomputer 26.

The channel selection microcomputer 26 reads the channel number data corresponding to the count data (frequency) from the correlation table of the EEROM 28 using the input count data as an address, for example. Then, the tuning microcomputer 26 causes the channel display 36 to display the channel number according to the read channel number data.

Thus, according to the embodiment of FIG. 1, the tuner unit
Even though the 12 channel selection method is the voltage synthesizer method, the channel number being received is automatically displayed as it is on the channel number display 36, so that the user can select the channel like the conventional voltage synthesizer method. Compared to the case where the number is determined and registered, erroneous settings are eliminated and the usability is greatly improved.

FIG. 2 is a block diagram showing another embodiment of the present invention. In contrast to the embodiment shown in FIG. 1 in which the AFT is applied to the local oscillator 18 by the SFT curve AFT voltage from the IF circuit (not shown), in the embodiment, such an AFT is directly counted by the digital AFT. It has been changed to the system type.

That is, the IF signal from the tuner unit 12 is amplified by the IF amplifier 40 included in the IF unit 38, and then detected by the PLL video detection circuit 42 to be a video detection output. Then, the output of the IF amplifier 40 is further given to the APC detection circuit 44. A PLL lock control circuit 46 is provided in the IF section 38, and a lock signal is given from the PLL lock control circuit 46 to the tuning microcomputer 26.

The output of the above-mentioned APC detection circuit 44 is given to a VCO (voltage controlled oscillator) 48 which constitutes a PLL, and this VCO 48 is controlled by a control voltage from a low pass filter 50.

The signal from the VCO 48 is given to one input (a) of the gate switch 56 through the VCO coil 52 and the buffer amplifier 54. The divided signal from the ECL prescaler 22 is applied to the other input (b) of the gate switch 56. The gate switch 56 is switched by a switching signal supplied from the tuning microcomputer 26, and the signal from the VCO 48 passing through the buffer amplifier 54 or the signal from the ECL prescaler 22 is selectively supplied to the counter 24. To be The count data of the counter 24 is the same as in the previous embodiment.
Given to 26.

In the embodiment of FIG. 2, when the user operates the search switch (not shown) of the operation unit 32 to perform the search operation, the tuning microcomputer 26 sets the gate switch 56 to the input (a) side. Switch. Therefore, the signal of the VCO 48 is given to the counter 24, and the frequency of the signal is counted by the counter 24. The count data of the counter 24 is given to the tuning microcomputer 26,
Therefore, the tuning microcomputer 26 controls the local oscillator 18 based on the count data, whereby the digital AFT operation is performed.

After tuning to the best tuning point in the tuner section 12, the tuning microcomputer 26 switches the gate switch 56 to the input (b) side. Therefore, the counter 24 counts the frequency of the divided signal from the ECL prescaler 22. Therefore, the tuning microcomputer 26 displays the channel number data on the channel display 36 based on the count data of the counter 24 at that time, as in the embodiment of FIG.

It should be noted that when the frequency of the local oscillator 18 is high, as in the UHF television channel, the ECL prescaler 2
If the frequency division ratio of 2 is switched and the frequency division ratio is increased, the number of bits of the counter 24 need not be increased so much. In this case, it will be necessary to clearly distinguish in the correlation table that the frequency data has a large frequency division ratio.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention. FIG. 2 is a block diagram showing another embodiment of the present invention. In the figure, 12 is a tuner section, 18 is a local oscillator, and 22 is an EC.
L prescaler, 24 is a counter, 26 is a microcomputer for channel selection, 28 is an EEROM, and 36 is a channel display.

Claims (1)

(57) [Claims] 1. A voltage synthesizer type receiver for controlling an oscillation frequency of a local oscillator of a tuner unit by a tuning voltage according to control data from a microcomputer, wherein the oscillation frequency of the local oscillator is divided by a predetermined division ratio. A frequency division means for frequency division, a counting means for counting the frequency division output from the frequency division means, and a correlation table of frequency and channel number data provided in association with the microcomputer, A voltage synthesizer type receiving apparatus, wherein the channel number of the receiving channel at that time is displayed by referring to the correlation table based on the count data from the counting means.